I hope that you have the other half of the claw mount which is mounted on the receiver. These mounts need to be hand fitted and be straight. Other than that, the other work is just restoration, assuming that head space is okay. Nice rifle and I would certainly consider restoring it, based on what I am seeing in the pictures.
I believe that there is a nice stock hiding there. My question is, how did it get that way? Tossed in a corner and left for years??? I hope it works out for you.
I do also think that there is a nice piece of wood under at of that grime. Sweat equity would most likely yield a really nice, classic, Mauser rifle if work is done patiently and properly. I have restored a couple of Mauser's that looked pretty bad , into something pretty nice with work and patience.